Stars and execs are flocking to these workouts of the moment, including the latest in sweat-drenching spinning.

Pain & Pleasure at the New David Barton Gyms

Bodybuilding impresario David Barton -- known for his stylish NYC and Miami gyms (members include Marc Jacobs and Sean Combs) -- is coming to Los Angeles with two gyms opening in February. Among his most popular classes is Pain & Pleasure, 45-minute group workout that focuses just on building muscles. Multiple sets target three muscle groups. His 35,000-square-foot Westside location (12100 W. Olympic Blvd.) will feature live DJs, while a 22,000-square-foot spot will open in Century City (1950 Century Park East). Membership rates aren't finalized.

Mission Possible at the Santa Monica Stairs

When she isn't on call 24/7 as Ben Stiller's on-set trainer, Jenna Phillips leads packs of aspiring actors through Runyon Canyon and groups of Palisades moms up and down the Santa Monica stairs in her 50-minute training sessions. The workouts include running, lunging, hiking, sprinting and resistance bands. "I like that it's outdoors," says Maureen Kenny, senior director for A&R at Columbia. Phillips is a walking advertisement for her regimen -- she was diagnosed with type
1 diabetes in 2000 but now says she is almost insulin-free. ($25 a session, jennaphillips.com)

Rev Cycling

Thanks to its location in the same building as WME Entertainment, the members-only Sports Club/LA is a top destination for execs and celebrities; group classes kick off at 6 a.m. to accommodate agents who want to squeeze in a workout before their first morning meeting. The newest pulse-pumping class is REV Cycling, which features Schwinn A.C. Performance bikes with a console that measures speed, distance, heart rate and calories burned. Sessions are 50 minutes. Katie Holmes, who attends REV three days a week, often brings along her stylist Jeanne Yang (also her partner in fashion brand Holmes & Yang) to talk shop. After that morning class, grab breakfast at Walter's, the hidden-away sandwich shop and unofficial WME commissary inside the building. (9601 Wilshire Blvd., Beverly Hills.)

ViPR at Equinox

The simple-looking ViPR tube forms the basis of a full-body workout at Equinox West Hollywood that's drawn the likes of Bradley Cooper. The hollow rubber tube, which has cutouts in the center that function as handles, can be held over the head, to the side or in front of the body while the user performs various core exercises including squats and jumping jacks with no breaks. (8590 Sunset Blvd.)